Today's high-powered and sensitive internal combustion engines have produced unique carburetion problems. Since most modern cars have low silhouettes, insulation under the hood, and restricted air ventilation over the engine, the tendency for temperature build-up in the carburetor is substantially increased, particularly when the engine is turned off after normal car operation. If the heat build-up is enhanced through conduction from the intake manifold to the carburetor, the problem is even greater, and hence the need for adequate gasket insulation from the intake manifold to the carburetor throttle body, and in some cases from the throttle body to the fuel bowl.
Along with the need to insulate the carburetor from engine heat is the need to provide a structure that will also effect sealability between the respective flanged parts in which the insulating structure is used. Thus, where it is desired to use an insulating structure between the throttle body and the intake manifold, due regard must be given to the provision of fluid-tight seals at the juncture surfaces of these components. Along with the insulating and sealability requirements for the above described structure or member, it is necessary to impart to that structure high torque retention characteristics so that, through long periods of usage under service conditions, the components of the carburetor assemblage will remain in fluid-tight relationship or are capable of being put back into such condition even when one component is removed from the other during various periods of servicing. The insulating-sealing structure must also possess the ability to perform these essential functions without creating distortion in mating metal parts between which it is placed, the metal parts usually being soft ductile materials, such as aluminum or zinc. By distortion is meant that, when an insulating-sealing structure is used between opposed flanged members, the bolting of one member to another with the insulating-gasket structure therebetween, bowing, arcing or other uneven mating of the components will result. Many times a structure that is clamped between two others produces a so-called spring effect, tending to distort one or both of the mating surfaces of opposed members. Obviously, distortion is quite undesirable in that it breaks the fluid-tight engagement or seal between opposed mating surfaces, and may also cause actual breakage of the throttle body adjacent to the bolt holes. To meet the aforedescribed criteria and overcome undesirable conditions found in today's automotive environment is the subject matter of this invention.
The prior art has suggested the use of one or more members for effecting thermal insulation, fluid sealing, torque retention and minimization of distortion in the highly sensitive carburetor bowl assembly of an internal combustion engine. However, for the most part, these suggestions have been unable to meet and satisfy all of the requirements necessary to provide insulating and sealing qualities, while maintaining high torque retention. Where one problem was solved, an undesirable one offset it, and the selective and independent control of the variables intrinsic to the overall problem was not obtainable. It is now believed that a gasket heat-insulating structure is available meeting all of the criteria dictated for satisfactory use in the carburetor assemblage, all of which is attained within economically feasible boundaries.